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A076144 Largest squarefree m <= sfn(n) such that m*sfn(n) is also squarefree, where sfn(n) is the n-th squarefree number. 2
1, 1, 2, 3, 5, 6, 7, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 26, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 46, 47, 51, 53, 55, 57, 58, 59, 61, 62, 65, 66, 67, 69, 70, 71, 73, 74, 77, 78, 79, 82, 83, 85, 86, 87, 89, 91, 93, 94, 95, 97, 101, 102, 103, 105, 106, 107, 109 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

gcd(a(n), spf(n)) = 1;

a(n+1) = sfn(n) for n < 106, but a(107) = 173 = sfn(105), as sfn(107)*sfn(106) = 177*174 = (3*59)*(2*3*29) is not squarefree.

The first n such that a(n+1) != A005117(n) (the squarefree integers) are 106, 258, 292, 368, 509, 515, 566, 653, 719, 807, 839, 882, 928, 992, .... - Emmanuel Vantieghem, Mar 10 2017

LINKS

Emmanuel Vantieghem, Table of n, a(n) for n = 1..1000

CROSSREFS

Cf. A005117, A077395.

Sequence in context: A325511 A240370 A193304 * A005117 A144338 A077377

Adjacent sequences:  A076141 A076142 A076143 * A076145 A076146 A076147

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Oct 30 2002

STATUS

approved

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Last modified October 17 19:24 EDT 2019. Contains 328127 sequences. (Running on oeis4.)